Permit to work
Permit to work explained: the authorisation behind high-risk jobs
A permit to work is a formal written authorisation allowing a specific high-risk job to start at a specific place and time, issued by a named authorised person only once the hazards are identified, the precautions and isolations verified in place, and the work party has confirmed it understands them. It controls when work may begin, not how to do it.
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The UK Health and Safety Executive describes it as "a more formal system stating exactly what work is to be done and when, and which parts are safe". The abbreviation PTW is near universal.
It closes the gap between two groups who each know half of what matters. Plant operators know what is live, pressurised, or happening nearby. The work party knows what it is about to do to it. Incidents cluster there, so the permit forces a documented conversation before tools come out. HSE is blunt about the limit: "the issue of a permit does not, by itself, make a job safe". It records that precautions were checked, not that they work.
Which activities need a permit to work?
The classic permit-controlled activities, each with its own permit type and checklist:
- Hot work. Welding, cutting, grinding, any ignition source near flammable material. Typically a gas test, combustibles cleared, and a fire watch during and after.
- Confined space entry. Tanks, vessels, pits, sewers, silos. Atmospheric testing, ventilation, an attendant at the entry, rescue plan ready first.
- Electrical isolation and live working. Proving dead, locking and tagging out, controlling the keys. Live working needs separate justification.
- Working at height. Fragile roofs, edge work, rope access, scaffold alteration.
- Excavation. Buried services, collapse risk, adjacent structures.
- Breaking containment. Line breaking and vessel opening on pressure or process systems.
- Others. Lifting over occupied areas, radiography, disabling safety systems, sometimes lone working in remote locations.
HSE's HSG250, "Guidance on permit-to-work systems", was written for the petroleum and chemical industries but is the reference text wherever permit systems operate.
Who signs a permit to work? The authorisation chain
This is what gets misunderstood most. A permit is not one signature. It is a chain of named roles, and the titles vary between organisations even where the functions do not.
- Applicant or performing authority. The contractor or supervisor who wants the work done. They request the permit and describe the task precisely.
- Area authority or plant owner. Responsible for that part of the site. They confirm the work fits with what else is happening and accept the operational impact.
- Isolating authority. A competent person who carries out and proves the isolations, applies locks and tags, and records them.
- Issuing authority or authorised person. Formally appointed, assessed as competent, named in the site's permit procedure. They verify every stated precaution is in place, then sign to issue. The pivotal signature.
- Acceptance. The person in charge of the work party signs to accept, confirming the crew is briefed and knows the limits.
- Suspension and handback. The permit is suspended or handed back when work stops, at shift end, or when conditions change.
- Cancellation. The issuing authority cancels it once work is complete, people are clear, and isolations can safely come off. The work party does not cancel its own permit.
Two rules hold that chain together: roles assigned without gaps or overlaps, and no one person holding two roles meant to check each other. HSE's human factors guidance lists clear responsibilities, accurate permit content, shift handover, training, and regular review.
How a permit to work differs from RAMS
- Risk assessment. What could go wrong on this kind of work and what controls are needed.
- Method statement. How the job runs step by step, controls built into the sequence. In UK practice the two go together as RAMS.
- Permit to work. Authorisation that this job may start now, here, under these verified conditions, for this duration.
RAMS are prepared in advance and cover the approach. A permit is issued on the day, expires, and is tied to conditions checked hours ago. RAMS approved three weeks back tell you nothing about whether the line is isolated this morning.
Permit to work in practice: a worked example
A contractor needs to weld a bracket in a plant room next to a fuel line. The area authority confirms no fuel transfer is scheduled. The isolating authority drains and locks off the adjacent section. The issuing authority walks the area, confirms the gas test, checks combustibles are covered and a fire watch set, then issues the permit for four hours. The supervisor signs acceptance and briefs the crew. Afterwards the fire watch runs on, and the issuing authority cancels the permit before isolations come off.
Where permit systems fail
- Signature without verification. A permit issued from a desk on the basis of what someone said, not from the work area.
- Scope creep. The job grows beyond what the permit describes. New scope needs a new permit.
- Poor shift handover. HSE notes that failures during isolation and reinstatement of process plant are a main cause of loss-of-containment incidents.
- Too many permits. Permitting routine low-risk work devalues the system and turns checking into paperwork.
- Confusing paperwork with control. The isolation is the control.
Does every country use permits the same way?
The principle is close to universal in high-hazard industry. The legal framing is not. In the UK, permit systems are the normal means of satisfying duties under the Health and Safety at Work etc Act 1974, the Confined Spaces Regulations 1997, the Electricity at Work Regulations 1989 and the Work at Height Regulations 2005, rather than being mandated by one named permit regulation. In the United States, specific OSHA standards mandate permit systems by name for permit-required confined spaces and control of hazardous energy. Requirements differ by country and industry, so the governing document is the site's own permit procedure plus the local regulator's rules, never a template from elsewhere. A field engineer on an unfamiliar site should ask which regime applies.
